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Table 2

Variables associated with Q fever seroconversion among 246 workers who were seronegative before culling small ruminants, the Netherlands, 2009*

Variable

No. (%) workers

Univariable analysis

Multivariable analysis†

Total

Seroconversion

RR (95% CI)

p value‡

RR (95% CI)

p value

Total

246 (100)

43 (17)

Sex

F

6 (2)

2 (33)

Reference

M

240 (98)

41 (17)

0.51 (0.16–1.64)

0.301

Age, y

<45

96 (39)

14 (15)

Reference

>45

150 (61)

29 (19)

1.33 (0.74–2.38)

0.339

2.0 (0.93–4.16)

0.07

Level of education

Low

39 (21)

5 (13)

Reference

Medium

103 (55)

18 (17)

1.36 (0.54–3.42)

High

44 (24)

8 (18)

1.42 (0.51–3.98)

0.765

Minimum distance of residence from nearest infected farm, km

>5

174 (73)

32 (18)

Reference

<5

63 (27)

9 (14)

0.78 (0.39–1.53)

0.460

Medical history§

No

128 (75)

23 (18)

Reference

Yes

42 (25)

5 (12)

0.66 (0.27–1.63)

0.358

Current or past smoker

No

84 (44)

16 (19)

Reference

Yes

108 (56)

16 (15)

0.78 (0.41–1.46)

0.435

Total hours worked inside farm perimeter¶

0–20

81 (33)

5 (6)

Reference

Reference

21–100

82 (34)

18 (22)

3.56 (1.39–9.12)

5.53 (0.71–42.77)

0.102

>100

80 (33)

20 (25)

4.05 (1.60–10.26)

0.003

7.75 (1.02–58.99)

0.048

Mean farm size >1,500 animals#

No

167 (68)

22 (13)

Reference

Yes

79 (32)

21 (27)

2.02 (1.18–3.44)

0.010

1.75 (0.93–3.30)

0.081

Worked mostly inside stable

No

110 (45)

11 (10)

Reference

Yes

133 (55)

31 (23)

2.33 (1.23–4.42)

0.006

2.58 (1.04–6.37)

0.040

Animal abortions on farm

No

208 (85)

33 (16)

Reference

Yes

38 (15)

10 (26)

1.66 (0.89–3.07)

0.119

0.93 (0.45–1.91)

0.844

Any previous culling experience

No

85 (43)

15 (18)

Reference

Yes

114 (57)

17 (15)

0.84 (0.45–1.59)

0.603

Adherence to hygiene and preventive measures**

Fully compliant

91 (50)

13 (14)

Reference

Not compliant

91 (50)

17 (19)

1.31 (0.68–2.53)

0.424

0.94 (0.51–1.72)

0.829

Months spent culling

Dec 2009–Mar 2010 only (mean temperature 3.2°C)

105 (54)

18 (17)

Reference

Apr–Jun 2010 only (mean temperature 13.9°C)

2 (1)

1 (50)

2.92 (0.69–12.41)

Dec 2009–Jun 2010

87 (45)

21 (24)

1.41 (0.80–2.47)

0.288

*Total for each category may be <246 because of missing data. RR, risk ratio; CI, confidence interval.†All data available for n = 180 in multivariable analysis.‡Pearson χ2.§History of cardiorespiratory disease, liver disorders, diabetes, cancer, immunosuppression, allergies, skin conditions.¶Data only available for n = 194, those who worked inside the farm perimeter.#Weighted mean number of animals on farms worked by participants.**Includes wearing mask, gloves, overalls, hairnet, showering after exposure.

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